There are conventionally known simplified steam amount measuring methods for measuring the amount of steam without using a steam flow meter. A first conventional method is directed for calculating the amount of steam by use of a direct fuel flow signal by a fuel flow meter. A second conventional method is directed for measuring an exhaust gas flow velocity in a flue based on a difference between a total pressure and a static pressure by a pitot tube, calculating a fuel flow rate, and estimating the amount of steam by use of an indirectly-calculated fuel flow signal. Both the first and second conventional methods are the methods for estimating the amount of steam based on the amount of input/output heat into/from a boiler.
The conventional methods for calculating the amount of steam based on the amount of input/output heat into/from a boiler as the first and second conventional methods have the following problem. That is, a temporally-changing velocity is different between a steam amount estimation based on the amount of input/output heat into/from a boiler and an actual steam amount measurement, and thus the ever-changing amount of steam cannot be measured without a response delay. For example, if a variation in intermittently supplied water, intermittent blow or supplied water temperature in a boiler occurs during a measurement, a temporal change in the amount of steam cannot be precisely measured (because a delay due to transmitted heat, accumulated heat or radiated heat is present).
The first and second conventional steam amount estimating methods have the problem that when a fuel property value such as the amount of generated heat, which is important data for estimating the amount of steam based on the amount of input/output heat into/from a boiler, changes, the estimated amount of steam changes. Particularly, in coal burning overseas, although it depends on the kind of coal, the amount of water has a large effect on outdoor crushed coal immediately before actual use, and thus the fuel property value changes. Therefore, the amount of generated heat and the amount of theoretical exhaust gas change and thus the estimated amount of steam changes.